While the idea of a solar powered car is attractive, the physical manifestation usually fails in both aesthetics and performance. Most of the solar-powered vehicles we’ve featured in the past are either extremely tiny, using the sun to charge up their electric batteries, or extremely awkward, with solar panels sprouting out from every available surface. But the folks at Missouri Sustainable Energy LLC aren’t interested in going down that road. Instead, they’re putting the sun to work through a technology we’re all too familiar with — the combustion engine. If successful, they could be on the road to a bright new future where the cost of solar energy drops by 75 percent.

Finding it hard to envision the mechanics that would allow the sun to power a conventional combustion engine? Don’t worry — it takes a little imagination. Inventors Matt Bellue and Ben Cooper (the creative minds behind the HydroICE project) say that instead of using gasoline to ignite a spark and thus moving a piston to create power, their engine would use the heating power of the sun.

“Take that same [combustion] engine and modify the variables slightly; instead of injecting gas/diesel, inject hot oil (using mirrored parabolic solar collectors, temperatures of 800 degrees farenheit can be reached!) into the cylinder,” explain the duo on the HydroICE project’s Indiegogo page. “Instead of a spark, add a few microdroplets of water. When the water contacts the hot oil, the oil’s thermal energy is transferred to the water and it instantly flashes to steam.” While you’re probably wondering how this could be integrated into a vehicle, a more immediate application could be as an off-grid source of electricity that could replace gas-powered generators.

It seems like science fiction but this unique, cleaner-burning engine is already on its way to becoming a reality. Bellue and Cooper have converted a 31cc 2-stroke gas engine to run as a HydroICE engine. They’ve also partnered with Missouri State University and the Missouri University of Science and Technology to develop all the necessary peripheral hardware (such as the solar collectors), and to test the engine’s efficiency.

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3 Comments

zeppflyerNovember 29, 2012 at 11:42 am

So, where is this concept left? As I see it, there are two niches:

Looking at automobiles, solar is out, but this engine could still be powered by kerosene, natural gas, or other fossil fuels. Then, the question becomes; “Can the hydroICE compete with existing steam engines and internal combustion engines in terms of weight, size, efficiency of fuel use, maintenance requirements, or emissions?”

Compared to the Doble automotive steam engines, which were just about the best ever built, this engine could probably be more compact, lighter, and require less maintenance, due to the lack of a boiler. Fuel economy would not be as good, and emissions would likely be higher.

Compared to a gasoline or diesel internal combustion engine, this would likely develop less power for an engine of given size and weight. The weight and size of condensers alone (which are vital if you don’t want to stop for water every few miles), means that steam engines will never compete with ICE in this category. Fuel consumption would likely be higher since ‘burning’ fuels simply contain less energy per unit of volume than ‘exploding’ ones. Thus CO2 emissions would also, likely, be higher. However, combustion in steam engines is far more efficient than in ICE’s, burning away nearly every other pollutant. (Jay Leno likes to quip that his 1929 Doble easily passes California’s strict air quality requirements.)

So, for cars, it’s questionable. What about for stationary solar thermal power generation?

Now, this design is, almost certainly, less efficient than an external-boiler steam engine for the reasons mentioned above. However, running and maintaining a boiler is far more complex than most people realize. So, in theory, this design could have an advantage for small, private, inaccessible solar-thermal installations, where peak efficiency is less important than initial cost, reliability, and ease of maintenance.

Vs. photo voltaic cells, the equation reverses. Obviously, solar thermal is more efficient than photo voltaic in some cases, otherwise, no one would be investing in solar thermal plants. It also has the advantage of being able to store power thermally, rather than in batteries to even out mismatches in supply and demand. This can be more efficient in terms of power loss over time, less expensive, and require less maintenance and control. Purchase and installation costs would also, probably, be lower. Whether the HydroICE, which would be less efficient than traditional steam, still maintains this advantage over photo voltaic remains to be seen. Furthermore, PV’s are getting more efficient all the time and have a lot more potential to grow in this regard than do mechanical means of turning sunlight into power.

On the other hand, with no moving parts or fluids to wear out or leak out, photo voltaic (disregarding storage) will always win the maintenance battle in the end. The only caveat to this is that, if something goes wrong with a PV panel, it’s almost certainly a ‘replace’, rather than a ‘repair’ job. These machines, on the other hand, could be repaired and reconditioned as they wore out, with far less infrastructure.

One other instance where PV’s can lose the maintenance battle is when they are being used primarily for direct mechanical drive, rather than to generate electricity for lighting, heating, refrigerating, etc. If we’re, say, running a water pump, rather than a house, the hydroICE, which would not require an additional step of an electric motor, might win the maintenance battle.

So, the most likely use for these engines is not in solar-powered cars, but in either conventionally-powered cars where emissions are a primary concern, or in stationary power gen that is REALLY far off the grid.

Overall, interesting tech, with some potential. Just not where the article claims that it might be.

zeppflyerNovember 29, 2012 at 10:56 am

Looking at the idea of a solar car; it just doesn’t work. In bright sunlight, about 100 watts fall on a square foot of ground. Assuming perfect efficiency, a Crown Vic, which is about as big as a car can practically be, could generate 19HP from sunlight. And that’s at 100% efficiency. Real life steam engines come in below 20% efficiency, so we’re already at about 4HP. This is before mechanical drivetrain losses, the fact that you’re not actually collecting 100% of those 100 watts, bad weather, NIGHT TIME, and losses in actually getting that heat from the sun to the engine.

But a car isn’t running all the time. What about storing energy for later use? Well, maybe, if you’re using good ol’ solar panels and batteries. If we were using this engine, solar energy would have to be stored in a heat sink, like at a thermal solar power plant. Only difference; a power plant has room for a giant vat of molten salt. A car doesn’t. Nor could it carry the weight. So, thermal solar is just not the way to go for a car, whether you are using the hydroICE or a traditional steam or Stirling-cycle engine.

zeppflyerNovember 29, 2012 at 10:37 am

As is typical with a lot of these solar-powered engines, the ’solar’ component is really irrelevant to the actual innovation and is probably just tacked on to make the thing more ’green’.

What we’re looking at here is a steam engine that flash-boils water in the cylinder, rather than in an external boiler. Where we get the heat to boil that water is irrelevant to the question of whether this motor is more efficient than a more traditional external-boiler steam engine (or turbine) at turning that heat into work. Again, that heat can come from the sun (as with the many thermal-solar power stations springing up in deserts around the world which use external boilers and steam turbines), but it could just as easily come from oil, coal, geothermal, or nuclear sources.

So, comparing apples to apples, I doubt that this motor would be as efficient as a steam engine with an external boiler. We have spent 400 years working on the efficiency of boilers and the simple fact that they are separated from the actual workings of the engine allows for a host of efficiency-increasing features which would be sacrificed in this design. Adding the hot oil as an intermediary heat exchanger also introduces an unneeded step in the process which would likely lead to some heat loss.

That’s not to say that there aren’t potential benefits, especially in an automotive setting. The lack of a boiler could drastically reduce size and weight, making this steam engine more practical for a car. It would, also, probably require less maintenance than an EC steam engine. It wouldn’t require as much of a warm-up period either. The final problem was mostly solved by the Doble flash boiler, but this is another good solution.